Brodie C
Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel.
Int J Dev Neurosci. 1994 Nov;12(7):631-40. doi: 10.1016/0736-5748(94)90015-9.
Platelet activating factor is a unique phosphoglycerine which possesses a variety of biological functions exerting its biological effects via specific surface receptors. In the central nervous system, platelet activating factor has been suggested to play a role during injury especially in conditions of ischemia and trauma-induced neuronal damage. The specific cell populations expressing platelet activating factor receptor, however, have not been identified. In this study, the binding properties of platelet activating factor receptors in C6 glioma cells and primary cultures of astrocytes and oligodendrocytes were characterized by using the ligand [3H]WEB 2086. Early-passage glial cells which exhibit oligodendrocytic phenotype, expressed lower levels of [3H]WEB 2086 binding than either late-passage cells which exhibit astrocytic phenotypes or primary astroglia cells. No specific binding was observed in primary cultures of oligodendrocytes. The Bmax (136 +/- 15.3 fmol/mg protein) and Kd (29 +/- 3.2 nM) levels obtained for primary astroglia cells were similar to those described for other cell types. The expression of platelet activating factor receptor in early-passage glia cells was up-regulated by treatment with insulin which induces astrocytic differentiation. In contrast, db-cyclic AMP exerted an inhibitory effect on the level of platelet activating factor receptor in both early- and late-passage cells. The level of functional platelet activating factor receptor in C6 cells as measured by the ability of platelet activating factor to induce 45Ca2+ influx was increased in cells expressing astrocytic phenotypes and was decreased in db-cyclic AMP-treated cells. In accordance with lack of specific [3H]WEB 2086 binding, platelet activating factor did not induce a detectable response of Ca2+ influx in cultures of oligodendrocytes. This report provides the first direct demonstration of selective expression of functional platelet activating factor receptors and their properties in astroglia cells. The findings support the suggestion that platelet activating factor may play an important role as a mediator of injury and immune responses in the nervous system.
血小板活化因子是一种独特的磷酸甘油，它具有多种生物学功能，通过特定的表面受体发挥其生物学效应。在中枢神经系统中，血小板活化因子被认为在损伤过程中发挥作用，尤其是在缺血和创伤诱导的神经元损伤情况下。然而，尚未确定表达血小板活化因子受体的特定细胞群体。在本研究中，通过使用配体[3H]WEB 2086对C6胶质瘤细胞以及星形胶质细胞和少突胶质细胞原代培养物中血小板活化因子受体的结合特性进行了表征。表现出少突胶质细胞表型的早期传代神经胶质细胞比表现出星形胶质细胞表型的晚期传代细胞或原代星形胶质细胞表达较低水平的[3H]WEB 2086结合。在少突胶质细胞原代培养物中未观察到特异性结合。原代星形胶质细胞获得的Bmax（136±15.3 fmol/mg蛋白）和Kd（29±3.2 nM）水平与其他细胞类型描述的水平相似。通过胰岛素处理诱导星形胶质细胞分化，早期传代神经胶质细胞中血小板活化因子受体的表达上调。相反，双丁酰环磷腺苷对早期和晚期传代细胞中血小板活化因子受体水平均产生抑制作用。通过血小板活化因子诱导45Ca2+内流的能力测量，C6细胞中功能性血小板活化因子受体水平在表现出星形胶质细胞表型的细胞中增加，而在双丁酰环磷腺苷处理的细胞中降低。与缺乏特异性[3H]WEB 2086结合一致，血小板活化因子在少突胶质细胞培养物中未诱导可检测到的Ca2+内流反应。本报告首次直接证明了功能性血小板活化因子受体在星形胶质细胞中的选择性表达及其特性。这些发现支持了血小板活化因子可能作为神经系统损伤和免疫反应介质发挥重要作用的观点。
